1. Field of the Invention
This invention relates to a vacuum cleaner, more particularly to a bypass-type motor protecting device for a vacuum cleaner.
2. Description of the Related Art
A conventional vacuum cleaner generally includes a bypass-type motor protecting device mounted upstream of a motor intake port such that, once a hose is clogged, the protecting device can be opened to permit flow of cool ambient air into a body housing of the cleaner over a suction motor.
Referring to FIG. 1, a conventional bypass-type motor protecting device is shown to include a casing 2 secured to a body housing 1 of a vacuum cleaner, a seat body 3 secured to the casing 2, a valve body 4 disposed to be movable in the casing 2, and a biasing member 5 disposed between the casing 2 and the valve body 4. The casing 2 has a tubular wall 202 which defines a passageway 201, and an inner abutment wall 204 which defines an internal port 203 that communicates the passageway 201 with an airflow duct 101 of the body housing 1. The seat body 3 extends radially to close an open end of the passageway 201, and defines a bypass entry port 301 communicating the passageway 201 with ambient air. The valve body 4 has a valve disc 401 which is movable to be engaged with or disengaged from the seat body 3. The biasing member 5 is disposed to bias the valve disc 401 to enable the valve disc 401 to be engaged with the seat body 3 so as to close the bypass entry port 301. Once a suction opening of the vacuum cleaner is clogged by the trapped dust, the valve disc 401 is moved and is caused to be disengaged from the valve seat 3 by ambient air pressure due to generation in the airflow duct 101 of a back pressure smaller than the ambient air pressure, so that external air is permitted to enter into the airflow duct 101.
The strength of the biasing force of the biasing member 5 must be precise, and must be measured in order to provide a good motor protecting effect without compromising the suction effect of the vacuum cleaner. However, no adjusting means is provided in the conventional bypass-type motor protecting device for adjusting the biasing force of the biasing member in a convenient and precise manner.